It's also important to clean your cases THOROUGHLY between loadings with black. The residue is just as corrosive to brass as it is to gun steel. My practice was to carry a milk jug 1/2 full of soapy water to the range, and drop the cases in as they were fired. Then when you get home, put them into a mesh bag and run 'em thru the washer-dryer. Just be sure they're fully dry when you load 'em into your tumbler.
Worked great for me in .44-40.

Larry